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Date of Award

Spring 2009

Document Type

Restricted Thesis: Campus only access

Degree Name

Bachelor of Science



First Advisor

Dr. Laura Runyen-Janecky


In several species of bacteria, the regulatory proteins OxyR and SoxRS control the response to oxidative and superoxide stress, respectively. Following construction of deletion mutations in the oxyR and soxRS genes in Shigella flexneri, a double mutant was made that lacked both genes. Under aerobic conditions, the ΔoxyR single mutant and the ΔoxyR ΔsoxRS mutant both grew to lower cell densities during exponential growth and had higher death rates during stationary phase as compared to either wildtype S. flexneri or the ΔsoxRS mutant. Under microaerobic conditions, the wildtype strain and the ΔoxyR- containing mutants grew to similar stationary phase cell densities, as did the ΔsoxRS mutant. In addition, both S. flexneri strains lacking oxyR demonstrated increased susceptibility to hydrogen peroxide as compared to the wildtype strain or the ΔsoxRS mutant. The S. flexneri strains lacking soxRS were more susceptible to the superoxide generator PMS as compared to the wildtype strain or the ΔoxyR mutant. Taken together, these data support a model in which OxyR is the most critical regulator in surviving oxidative damage during aerobic growth in S. flexneri.